Remove `request`.

Summary:
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**Summary**
Remove `request` from `metro`.  It doesn't seem to be used.
<!-- Explain the **motivation** for making this change. What existing problem does the pull request solve? -->

**Test plan**
Everything works as it did before.
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Closes https://github.com/facebook/metro/pull/151

Differential Revision: D7226502

Pulled By: rafeca

fbshipit-source-id: fc353292ba55ea9f98eba67f05f8f8f82794dd82

packages/metro/package.json

@@ -84,7 +84,6 @@
     "mime-types": "2.1.11",
     "mkdirp": "^0.5.1",
     "node-fetch": "^1.3.3",
-    "request": "^2.79.0",
     "resolve": "^1.5.0",
     "rimraf": "^2.5.4",
     "serialize-error": "^2.1.0",

yarn.lock

@@ -4863,7 +4863,7 @@ request@2.81.0:
     tunnel-agent "^0.6.0"
     uuid "^3.0.0"
 
-request@^2.79.0, request@^2.83.0:
+request@^2.83.0:
   version "2.83.0"
   resolved "https://registry.yarnpkg.com/request/-/request-2.83.0.tgz#ca0b65da02ed62935887808e6f510381034e3356"
   dependencies: